Curable thiol-ene compositions for optical articles

Abstract

Curable thiol-ene compositions containing urethane (meth)acrylate oligomers that are readily polymerized to produce optical articles and coatings are described.

Description

FIELD OF THE INVENTION[0001]The present invention provides curable thiol-ene compositions containing urethane (meth)acrylate oligomers that are readily polymerized to produce optical articles and coatings.BACKGROUND OF THE INVENTION[0002]Radiation curable compositions containing carbon-carbon unsaturated monomers and polythiols were developed in the early 1970s. U.S. Pat. No. 4,234,676 (Hein et al.) describe a composition comprising a carbon-carbon unsaturated polymer, a crosslinkable monomer, a polythiol, and curing agent directed primarily at printing plate production.[0003]U.S. Pat. No. 4,808,638 (Steinkraus, et al) describes a composition comprising a norbornene resin, polythiol, and free radical initiator that can be photocured in visible light when an iron arene complex is present.[0004]U.S. Pat. No. 4,139,385 (Crivello) describes a composition comprising a polyolefin, polythiol, and onium salt photoinitiator. The films, 75 micrometers thick (3 mil), were curable by a cationic...

AI Technical Summary

Benefits of technology

[0006]The present invention includes a photopolymerizable composition comprising an aliphatic urethane (meth)acrylate oligomer, a polythiol, optionally a reactive diluent, and optionally a photoinitiator. The inventive composition can be made free of solvent and unreactive species and can be rapidly photocured. The composition, when cured is non-yellowing, exhibits low shrinkage and low birefringence making it suitable for many optical applications such as optical lenses, optical fibers, prisms, light guides, optical adhesives, and optical films.

[0008]Advantageously, the present invention provides curable compositions that are readily melt processible without appreciable monomers, reactive diluents and photoinitiators. Curable systems containing a significant amount of solvent, monomers and reactive diluents can give rise to a significant increase in density when transformed from the uncured to the cured state causing a net shrinkage in volume. As is well known, shrinkage can cause unpredictable registration in precise molding operations such as those required in manufacture of optical elements such as lenses. Shrinkage can also create residual stress in such optical articles, which can subsequently lead to optical defects, including high birefringence.

Problems solved by technology

Curable systems containing a significant amount of solvent, monomers and reactive diluents can give rise to a significant increase in density when transformed from the uncured to the cured state causing a net shrinkage in volume.

As is well known, shrinkage can cause unpredictable registration in precise molding operations such as those required in manufacture of optical elements such as lenses.

Shrinkage can also create residual stress in such optical articles, which can subsequently lead to optical defects, including high birefringence.

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